The invention is in the field of luminous displays and signs, and more particularly relates to gas plasma display devices.
The production of light by the passage of electricity through gases is a well known phenomenon. Devices utilizing this phenomenon have been widely developed in the form of plasma display devices which display specific numerals, characters, symbols, graphics, and the like. The neon sign is an example of a gas discharge display device, typically including an elongated glass tube filled with neon and a pair of excitation electrodes disposed at opposite ends of the tube. In this example, the rigid tube, or envelope, defines the shape of the illumination pattern. This shape is established at the time of manufacture, and cannot be changed.
Other prior art gas discharge display devices may include a plurality of shaped character electrodes in direct or close contact with an electroluminescent gas within a glass envelope, for example, Nixie tubes. In such devices, selected ones of the shaped electrodes may be energized to obtain a desired character display. Again, the shape of the illumination is predetermined by the shape of the electrode which is established at the time of manufacture of the device.
Still other forms of prior art gas discharge display devices include dielectric-bounded, gas-filled character-shaped channels within an envelope, with a suitable set of energizing electrodes. As in U.S. Pat. No. 3,621,332, a plurality of such channels may be established within a single envelope, with electrodes being arranged for selective activation of one channel at a time. Alternatively, as in U.S. Pat. No.4,584,501, a single elongated channel may be formed in one plate of a two glass plate sandwich arrangement, with energizing channels in an adjacent plate. All of these arrangements are suitable for displaying indicia, but as with the earlier discussed prior art, the shape of the display, i.e. the channel configuration, is determined at the time of manufacture of the device.
Yet other prior art gas discharge devices include generally similar display configurations, but have an addressable matrix in which selected dot regions may be selectively energized. For example, as shown in U.S. Pat. No. 4,035,690, selected ones of overlapping orthongal sets of electrodes may be energized to generate a desired dot matrix character. In that patent, the electroluminescent gas is confined to the interior of a plurality of dielectric spheres disposed between the sets of electrodes. With the dot addressible matrix, substantial flexibility is provided in that any dot pattern graphics may be displayed, for example using conventional bit-mapped graphics techniques. However, as with the other above mentioned prior art, all possible display patterns, i.e. the electrode overlap regions, are established at the time of manufacture of the device.
Yet another form of prior art gas discharge device is disclosed in U.S. Pat. No. 3,629,654. As shown in that patent, a pair of opposed, spaced apart plates are mutually sealed at their perimeter to establish an electroluminescent gas filled cell. A transparent conductive coating is disposed on one outer surface of the cell. A movable external sheet having predetermined shaped conductive regions is pressed against the other outer surface of the cell and an ionizing signal is applied across the conductive coating and the conductive region of the external sheet to generate a visible discharge in the cell having the shape of the conductive regions of the external sheet. This two-element display thus requires a means for positioning the external sheet relative to the cell in order to establish an image.
It is an object of the present invention to provide an improved plasma display device.
Another object is to provide an improved plasma display device which may be user-programmed for the display of a desired image.
Yet another object is to provide an improved plasma display which may be economically and efficiently configured to display a desired image.